Common causes of electronic device failures are microcracks or voids that form in a part of the electronic device, such as a semiconductor chip, particularly in stressful environments. Such microcracks or voids can allow introduction of impurities into the electronic device. Application of a sputtered metal or metal oxide coating on electronic devices can provide a barrier against microcrack or void development. Such a sputtered coating can provide a barrier against introduction of ionic impurities, such as chloride ion and sodium ion that can disrupt transmission of electronic signals. Application of such a sputtered coating to the electronic device can also provide some protection against moisture and volatile organic chemicals.
Other articles can have an outer layer or coating of metal or metal oxides. For example, various optical substrates can be coated with one or more layers of metal oxides to reduce glare and reflection of light. Such optical substrates include those used in doors, windows, picture frames, optical lenses, filters, display devices (e.g., display panels of electronic devices), and the like.
Metal or metal oxide coatings are generally durable and uniform. However, some metal or metal oxide layers made by common techniques, such as sputtering processes, are relatively porous and contain clusters of particles that form a relatively rough profile. Sputtered metal or metal oxide coatings tend to have a high surface energy making these materials prone to contamination by impurities from a variety of potential sources such as fingerprints. Articles having such coatings can be difficult to clean without the use of solvent-based cleaners, some of which are environmentally undesirable. Additionally, removal of surface contaminants can detrimentally affect desired properties of the metal or metal oxide surface if the cleaning process leaves residue behind.
Numerous attempts have been made to provide anti-soiling characteristics to metal or metal oxide surfaces. Some attempts have focused on providing these characteristics to the metal or metal oxide layer itself, while other attempts have focused on providing an anti-soiling coating over the metal or metal oxide surface. Such anti-soiling overcoats can be monolayer films that are free of low molecular weight impurities. Low molecular weight or soft materials are generally considered undesirable because these materials can adversely affect the anti-soiling characteristics of the overcoat. Some existing overcoats that are capable of providing adequate anti-soiling characteristics to electronic components include compounds that are based on seven-carbon and eight-carbon perfluoroalkyl groups. However, some of these compounds are losing favor as possibly being environmentally undesirable.
The technique for applying the anti-soiling overcoat to the substrate can also be problematic, depending on the composition of the particular overcoat. For example, conventional application methods for some anti-soiling overcoats entail application of excess coating material that is removed to maintain desirable characteristics of the metal or metal oxide-containing substrate. Such methods typically require a post-treatment step such as polishing or solvent washing. In general, such post-treatment steps are undesirable to manufacturers because such post-treatment steps can increase costs, can involve use of additional solvents, can increase the chance of degrading the metal or metal oxide-containing substrate, or combinations thereof.